On Ajax Page call only buttons the head and body are coming two times. we wont need it. You can directly call javascript and
<script type="text/javascript" src="http://w.sharethis.c...s.js"></script>
<script type="text/javascript">stLight.options({publisher: "168fe05d-a490-44f1-91b8-e1f5c9cb131d", shorten:false});</script>